Micro/nanoporous polymer chips as templates for highly sensitive SERS sensors

Abstract

High-throughput, simple nanofabrication methods are essential keys for involving plasmonic materials with large electric fields for practical applications. We demonstrate in this paper a facile route for fabricating multifunctional metallic nanomaterials for sensing, which is particularly relevant to SERS spectroscopy. A simple deposition of a polymer dispersion doped with metallic precursor onto a conducting substrate allows a spontaneous formation of SERS-active substrates via vapor induced phase separation. The process enables the fabrication of several kinds of SERS chips with an original combination of fast throughput, low cost, reproducibility and high sensitivity. Our SERS results show significant enhancement factors exceeding 10¹³, which match the largest value (10¹⁴) of metallic nanoparticle aggregates found until now. We quantify these enhancements by depositing bipyridine ethylene (BPE) on the substrate and spatially mapping their Raman intensities using confocal micro-Raman spectroscopy. Both the sensitivity threshold and reproducibility of all substrates were estimated by SERS measurements at variable concentrations of BPE. Our approach is new in fabricating high-throughput and reproducible SERS substrates over a large surface (on the whole substrate) by a one-step technique. As a result, we demonstrate a novel class of SERS substrates for which no patterning is necessary as in lithography, which provide a quick, simple and cheap way to fabricate highly sensitive SERS substrates.